Spring devices – Vehicle – Comprising compressible fluid
Reexamination Certificate
1999-04-07
2001-05-22
Oberleitner, Robert J. (Department: 3613)
Spring devices
Vehicle
Comprising compressible fluid
C267SDIG002
Reexamination Certificate
active
06234462
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates hydro-pneumatic spring struts and more particularly, to a self-pumping hydro-pneumatic spring strut with internal leveling.
2. Description of the Related Art
Spring struts of this kind are already known (for example, DE 33 06 393 C1), in which the throttle is formed by an orifice between a valve body of the suction valve and that end face of a sleeve which faces said valve body. Between the throttle and the bleed orifice, the inner wall of the pump rod is utilized as a bleed duct. Pressure equalization between the high-pressure chamber and the low-pressure chamber takes place, initially, via the relatively large bleed orifice insensitive to dirt, along the bleed duct, through the throttle and, from there, centrally through the pump rod. Since the throttle is mounted between the suction valve plate and the end-face valve seat of the sleeve, there is virtually no risk of the throttle being clogged by particles in the damping medium. This is due to the valve plate being lifted from its seat, which results in the throttle being opened constantly and being flushed free by the damping medium. However, a design of this type is complicated and the individual pump rod lengths, together with their sleeves of correspondingly differing length, in each case have to be adapted to the overall length of the spring strut. This means that, in different instances of use, spring struts of different length are also employed, which in each case require a corresponding pump rod. Furthermore, the dimensional accuracy of the sleeve and of its receiving bore in the pump rod must be made perfect, and, since the valve plate which, together with the end face of the pump rod, forms the control edges, re-machining or cutting of the control edges is necessary after the sleeve has been installed in the pump rod.
SUMMARY OF THE INVENTION
An object of the invention is to provide a simple, functionally reliable and insensitive spring strut, in which, while the prolonged bleed time is preserved, the bleed device can easily be produced under a series of conditions and which can be used, irrespective of the length of the pump rod, of the pump cylinder or of the piston rod.
This and other objects are achieved according to the invention, in that a non-return valve is arranged parallel to the throttle, through which the flow can pass from the low-pressure chamber in the direction of the pump cylinder.
It is advantageous, at the same time, that the throttle and the non-return valve are designed independently of the respective construction and can be arranged at any desired location between the low-pressure chamber and the pump cylinder. The parallel connection of the throttle and non-return valve affords the further advantage that the oil can flow through, throttle-free, in the suction direction and, throttled, in the discharge direction.
According to a further embodiment, there is provision for the throttle and the non-return valve to form a common structural part. It is advantageous, in this case, that the throttle and non-return valve can be produced as a pre-assembled structural unit which can then be introduced as a unit into the appropriate position when the spring strut is being assembled.
According to a further embodiment, a cross-sectional narrowing is provided as a throttle. In an embodiment which favors manufacturing, a platelike elements is provided as a non-return valve which is controlled into one of the two possible end positions by the flow of the oil. Advantageously, in this case, the platelike element is loaded on at least one side by a spring.
In order to achieve sufficient axial guidance on the outer wall and, at the same time, obtain corresponding flow cross sections, the platelike element has a circumference that is not round.
According to another embodiment which favors manufacturing, a recess in the pump rod is provided as a throttle.
According to yet a further embodiment, there is provision for the platelike element to cooperate with the end face of the pump rod. Advantageously, in this case, in order to form the throttle, a recess is provided between the end face of the pump rod and the platelike element.
In a preferred embodiment, the non-return valve is provided as a ball which is controlled into one end position or the other by the flow of the oil.
If the throttle and non-return valve are used in a common structural part, there is provision, according to an essential feature, for the structural part to be received within the pump rod.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
REFERENCES:
patent: 2436573 (1948-02-01), Heynes
patent: 3110485 (1963-11-01), Axthammer
patent: 4577840 (1986-03-01), Meller et al.
patent: 5941508 (1999-08-01), Murata et al.
Beck Hubert
Kuchheuser Werner
Wortmann Willi
Cohen & Pontani, Lieberman & Pavane
Mannesmann Sachs AG
Oberleitner Robert J.
Siconolfi Robert A.
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